Whatever you do,安全 is the most importantWhatever you do,（安全） is the most important我填的是 safety

Whatever you do,安全 is the most importantWhatever you do,（安全） is the most important我填的是 safety
Whatever you do,安全 is the most important
Whatever you do,（安全） is the most important
我填的是 safety

Whatever you do,安全 is the most importantWhatever you do,（安全） is the most important我填的是 safety
完全正确

对。
这里需要填一个名词
而safty是名词。

对的，就应该是名词形式